During a traditional electrocardiographic (ECG) exercise test, doctors cannot look back at historical ECG data. They can only see the data at the current moment. Once a doctor misses an abnormal waveform, he cannot retrieve the past data again for analysis during the test. He can only wait until the end of the test, and then analyze the final report. Besides, doctors are not able to see the changing tendency of the heart rate or the changing tendency of the exercise intensity during the test.